Alternatives

As an alternative to the semianalytic function,
invoke the BERTool GUI (bertool) and use the Semianalytic tab.

Description

ber = semianalytic(txsig,rxsig,modtype,M,Nsamp) returns
the bit error rate (BER) of a system that transmits the complex baseband
vector signal txsig and receives the noiseless
complex baseband vector signal rxsig. Each of these
signals has Nsamp samples per symbol. Nsamp is
also the sampling rate of txsig and rxsig,
in Hz. The function assumes that rxsig is the input
to the receiver filter, and the function filters rxsig with
an ideal integrator. modtype is the modulation
type of the signal and M is the alphabet
size. The table below lists the valid values for modtype and M.

Modulation
Scheme

Value
of modtype

Valid Values of M

Differential phase shift
keying (DPSK)

'dpsk'

2, 4

Minimum shift keying (MSK)
with differential encoding

'msk/diff'

2

Minimum shift keying (MSK)
with nondifferential encoding

'msk/nondiff'

2

Phase shift keying (PSK)
with differential encoding, where the phase offset of the constellation
is 0

'psk/diff'

2, 4

Phase shift keying (PSK)
with nondifferential encoding, where the phase offset of the constellation
is 0

'psk/nondiff'

2, 4, 8, 16, 32, or 64

Offset quaternary phase
shift keying (OQPSK)

'oqpsk'

4

Quadrature amplitude modulation
(QAM)

'qam'

4, 8, 16, 32, 64, 128, 256,
512, 1024

'msk/diff' is
equivalent to conventional MSK (setting the 'Precoding' property
of the MSK object to 'off'), while 'msk/nondiff' is
equivalent to precoded MSK (setting the 'Precoding' property
of the MSK object to 'on').

Note:
The output ber is an upper bound on
the BER in these cases:

DQPSK (modtype = 'dpsk', M =
4)

Cross QAM (modtype = 'qam', M not
a perfect square). In this case, note that the upper bound used here
is slightly tighter than the upper bound used for cross QAM in the berawgn function.

When the function computes the BER, it assumes that symbols
are Gray-coded. The function calculates the BER for values of Eb/N0 in
the range of [0:20] dB and returns a vector of length 21 whose elements
correspond to the different Eb/N0 levels.

Note:
You must use a sufficiently long vector txsig,
or else the calculated BER will be inaccurate. If the system's impulse
response is L symbols long, the length of txsig should
be at least ML. A common
approach is to start with an augmented binary pseudonoise (PN) sequence
of total length (log2M)ML.
An augmented PN sequence is a PN sequence with
an extra zero appended, which makes the distribution of ones and zeros
equal.

ber = semianalytic(txsig,rxsig,modtype,M,Nsamp,num,den) is
the same as the previous syntax, except that the function filters rxsig with
a receiver filter instead of an ideal integrator. The transfer function
of the receiver filter is given in descending powers of z by the vectors num and den.

ber = semianalytic(txsig,rxsig,modtype,M,Nsamp,EbNo) is
the same as the first syntax, except that EbNo represents Eb/N0,
the ratio of bit energy to noise power spectral density, in dB. If EbNo is
a vector, then the output ber is a vector of the
same size, whose elements correspond to the different Eb/N0 levels.

ber = semianalytic(txsig,rxsig,modtype,M,Nsamp,num,den,EbNo) combines
the functionality of the previous two syntaxes.

[ber,avgampl,avgpower] = semianalytic(...) returns
the mean complex signal amplitude and the mean power of rxsig after
filtering it by the receiver filter and sampling it at the symbol
rate.

Examples

Limitations

The function makes several important assumptions about the communication
system. See When to Use the Semianalytic Technique to find out
whether your communication system is suitable for the semianalytic
technique and the semianalytic function.